Caret disappear when TextBox got focus using Keyboard

[na2axl]

Sorry, I don't know if the issue title is right. I encounter an issue when I'm using the Keyboard (the Tab key) to navigate over TextBoxes, but when a text box got focused by this way, the caret doesn't appear, but the text box is focused.

An example:

1. Create a Grid or any other Panel with many TextBoxes in it.
2. Click on the first TextBox, the caret appear, the TextBox is focused.
3. Press the Tab key to navigate to the next TextBox:
   a. If this TextBox has no content, the caret appear, the TextBox is focused;
   b. If this TextBox already has a content, the whole content is selected, the caret doesn't appear, the TextBox is focused. Clicking on this TextBox don't make the caret appear (I think is because the TextBox is already focused). The content can be edited but without caret.
4. The same behavior in 3 is reproduced for next and previous TextBoxes when continuing the Tab navigation.